This invention relates generally to apparatus for mixing and dispensing multi-component foam or fluid products, and relates more particularly to purgeable spray guns for urethane foam.
The use of sprayed urethane foams is rapidly expanding in construction, insulation and packaging industries. This relatively inexpensive product has proved to be a highly valuable insulating and packaging material for a number of reasons. Its resiliency, high compressive strength and its excellent dimensional stability make it an excellent packing material for shipping relatively fragile items in cartons where rough handling may be encountered. It has extremely low heat-transmitting properties, making it an excellent insulation material. Relatively extreme temperatures do not greatly affect it. It does not deteriorate rapidly, thus providing a long service life.
Further, urethane foam can be easily prepared and then applied or emplaced in an almost limitless variety of desired locations. The several fluid components of urethane foam are often stored separately, and then are mixed on the job site to create the foaming product. This mixed, foaming product is then discharged or sprayed into a desired location or target area. After application, the foam hardens into a light, strong protective and insulative covering. Devices which have been used with great success in mixing and supplying urethane foam are disclosed in Brooks U.S. Pat. Nos. 3,559,890 and 3,633,795.
Experience has shown that the components of urethane foam can be selected so as to provide a relatively quick-hardening product fluid. After the material is sprayed on or into the target area, foam product solidification begins. Now, this solidification occurs not only in the desired target area, but in residue product which may remain within the dispensing gun after spraying has been stopped. Residue foam product which has hardened inside parts of the gun make gun cleansing and subsequent use difficult. This problem has been met with great success by foam dispensing guns such as those disclosed in Brooks U.S. Pat. Nos. 3,633,795 and 3,784,110. In these devices, the foam gun is provided with a nozzle inside which the foam product constituents are mixed, and from which the mixed foam product is dispensed. After gun use, the nozzle can be removed, and a fresh nozzle installed.
Recently, the use of urethane foam as an insulation and packing material has found increased favor in applications providing target areas of restricted size and shape. When workers are dealing with such restricted target areas, they often find it necessary to spray or apply the foam in an intermittent manner. For example, a layer of foam may be initially applied to the restricted target area, and then foam spraying is halted while the worker inspects the target area; after inspection, another foam layer is applied. In another case, the worker may be forced to temporarily halt foam spraying while either he or a co-worker place an object to be shipped within a carton or other container. After object emplacement, foam applying operations can be resumed. As the container is filled, spraying operations may necessarily again be halted while inspection of the finished packing operation is undertaken. The carton is then closed, is removed, and a new empty carton is placed at the work station for spraying and packing.
Under such circumstances, it may be inconvenient to remove and replace a spray gun nozzle after each short spraying operation. A number of short spraying operations may be required during a single packaging or insulating job, and repeated nozzle replacement can add to costs, and can delay production.
While relatively short time lapses between sprayings can, under some circumstances, be tolerated without foam set-up and gun clogging, time lapses of greater duration permit the fluid constituents to either completely or partially solidify within the gun components, thereby completely or partially clogging the gun. Poor gun performance and an insulation or packing job of degraded quality result. Worker annoyance and hurried efforts can also occur, and can indirectly contribute to a finished product of less than maximum quality.
This problem of partial gun clogging during intermittent spraying operations can be minimized or eliminated by purging those parts of the gun wherein the fluid components are comingled, mixed and discharged with a nonreactive purge fluid. A gun of this general type is shown in U.S. Pat. No. 2,991,015 to Standlick. In addition, purging the gun permits use of fluid components which form a relatively fast-setting product not practically accommodated in other types of guns or dispensing systems.
It is an object of the present invention to provide an improved dispensing gun for mixing and discharging fluids such as urethane foam.
Another object is to provide a fluid mixing and dispensing gun wherein the problem of fluid solidification within the gun can be economically minimized or obviated even when the gun is used intermittently during short, spaced apart periods.
Yet another object is to provide a spray gun which permits purging settable product fluid constituents from important gun parts.
Still another object of the invention is to provide a dispensing and spraying gun for polyurethane foam and like products wherein relatively complete purging of both the nozzle and relatively upstream gun portions is assured. A more specific object is to provide a dispensing gun for urethane foam and like fluids wherein the fluid components and product can be easily and quickly purged from gun valves, the mixing nozzle and other parts thereby obviating clogging.
Yet another object of the invention is to provide a gun for mixing and spraying polyurethane foam and like fluids which can be easily purged when the gun is being used for intermittent spraying, and which is provided with a nozzle member which can be easily removed and quickly replaced after the completion of major-length spraying operations.
A further object is to provide a gun of the described kind which is inexpensive in initial cost, and which can be easily and effectively operated by even inexperienced personnel.
And a further object of the invention is to provide a mixing and dispensing gun for polyurethane and like products wherein interaction of the respective components is positively restricted to a disposable or reconditionable nozzle.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings. Throughout the drawings, like reference numerals refer to like parts.